1. Field of the Invention
The present invention relates to a helicotoroidal vane internal combustion rotary engine for use in applications that utilize an internal combustion design. As discussed more fully below, the term "helicotoroidal vane" refers to the path that the vane follows on the inner surface of a rotor casing, as the vane rotates about an axis that is non-parallel to the axis of rotation of the rotor. The vanes, in effect, follow a "helix-around-a-torus" path within the rotor troughs. The term "toroidal" or "torus" refers to a ring shaped apparatus. Certain features of the present invention may be utilized in compressor designs as well.
More particularly, the invention relates to a helicotoroidal vane engine where air-fuel volumes are physically isolated through the compression/combustion/expansion cycle, as in a positive displacement engine, and the design is inertially balanced without any reciprocating members, as in a turbine engine.
2. Description of the Related Art
The overall invention relates to the class of devices known as internal combustion engines. Internal combustion engines produce mechanical power from the chemical energy contained in the fuel, this energy being released by burning or oxidizing the fuel internally, within the engine's structure.
Practical devices currently include piston engines, Wankel engines, reciprocating vane engines, and turbine engines. These current engine types may be broken down into two fundamental categories: positive displacement engines and turbine engines.
In a positive displacement engine the flow of the air-fuel mixture is segmented into distinct volumes that are completely or almost completely isolated by solid sealing elements throughout the combustion cycle, creating compression and expansion through physical volume changes within a chamber. Combustion in such a positive displacement arrangement is described as occurring at constant volume.
Turbine engines, however, rely on fluid effects to create compression and expansion, without solidly isolating chambers of the air-fuel mixture. Combustion in turbine engines is described as occurring at constant pressure. Although at a given compression ratio, the constant volume (positive displacement) ideal cycle is inherently more fuel-efficient than the constant pressure (turbine) ideal cycle, real world constraints set by current design shortcomings usually result in the opposite efficiency ranking order.
There are trade-offs associated with the selection of a particular engine design. For example, turbine engines suffer substantial efficiency losses at partial power settings, a drawback which has prevented their practical use in automobiles to date. On the other hand, the reciprocating motion of the positive displacement engine introduces inertial forces which invariably produce friction and mechanical stresses that must be countered by lubrication. Taken together, these reciprocation effects result in designs with low efficiency, high pollution emissions, and low power density (power to weight and power to size ratios). Thus, current embodiments of both turbine and positive displacement designs suffer shortcomings.
In seeking to eliminate the reciprocating motion from the positive displacement design, some engine designers have advocated the so-called "rotary" engine designs, such as the Wankel design or conventional vane engine design.
However, the Wankel and conventional vane engines are not true rotary engines in the sense implied, i.e., lacking the reciprocation of the piston engine. All of these rotary positive displacement devices fundamentally rely on reciprocation to generate volume changes. The reciprocation of these rotary engine designs may not be visually obvious at first as with the piston design, because the elements in the Wankel and vane designs combine the reciprocation with rotary motion, whereas the piston design separates the reciprocating motion of the piston from the rotary motion of the crankshaft. Combining the reciprocating and rotary motions, however, does not sidestep the inherent reciprocation shortcoming of current positive displacement designs.
If it were possible to extract the best potential aspects of the positive displacement and turbine engines, a design would emerge which would include, among others, the following features:
(1) Positive displacement design PA1 (2) Zero reciprocating motion PA1 (3) Fast combustion cycle PA1 (4) High compression and expansion pressure ratios PA1 (5) Lean fuel-air ratio PA1 (6) Zero oil lubrication in engine chamber
These features have certain advantages for engine designers. For example, a fast combustion cycle would reduce NOx pollution emissions. Furthermore, the high compression and expansion pressure ratios would allow lean fuel-air mixtures to be reliably ignited and reacted. This lean mixture would in turn keep peak gas temperatures down low enough to minimize NOx pollution emissions and permit the utilization of existing high temperature ceramic materials which could withstand the peak temperatures, thereby eliminating the need for an efficiency-robbing cooling system. The lack of reciprocating forces would further provide an acceptable low-stress environment to utilize the existing high-temperature ceramic materials.
In addition, the design would permit utilization of air-bearings, which would eliminate all liquid or solid lubricants from the combustion chamber, further reducing pollution emissions. The lack of oil lubrication would permit high-temperature, uncooled operation, which would enhance longevity and reliability.
The efficiency of such an engine would be optimized by the high compression and expansion ratios, the lack of an energy-robbing cooling system and the lean fuel-air ratio.
In addition to the stated factors which reduce the percentage of emissions, the increased thermal efficiency of such an engine would lower absolute levels of all pollutants for any given energy output. Even CO.sub.2, a necessary by-product of hydrocarbon combustion, would decrease in absolute levels, simply by virtue of the increased thermal efficiency.
The combination of a positive displacement design without any reciprocating motion would allow fast combustion cycles at fast flow velocities, operating with all forces virtually perfectly balanced. This would result in an extremely high power density, thereby allowing the lean fuel-air ratios to be used while at the same time reducing weight. A reduction in weight would permit the use of smaller quantities of the advanced ceramic materials necessary for high temperature, uncooled operation-without incurring undue costs. Such a "Positive Displacement Turbine" engine would combine the partial power efficiency advantages of positive displacement engines with the high power density, balanced, and smooth-running design of turbine engines. Such a design would yield high fuel efficiency and low pollution emissions at all power settings.
Therefore, a need exists for an internal combustion engine that seeks to optimize certain performance characteristics of both the positive displacement and turbine engines.